hp 28s yellowed keys.

[rprosperi]

My opinion, which likely is no help at all is this: If feeling that your unit, which may be slightly darker than a typical unit, bothers you, then I think the result of any chemical treatment, which will inevitably produce inconsistent / uneven coloration, would really, really bother you.

Maybe just think of your unit as a "rare, slightly darker-themed HP-28S" and take comfort in knowing it's a rare model with unusually even colored aging?

Published results of such chemical treatments typically only produce good, even color lightening on large, flat, even surfaces, and is almost certain to have uneven results on such a complex surface as 50+ keys, bezel, etc. And that's a best case scenario if the chemicals don't do any internal damage.

As I said, likely not helpful....